i have heard the 3rd gen cranks have better factory balancing than the previous models. A friend of mine that talked to a cummins engineer told him that. take that for what it is worth. I use 3rd cranks and just have the gear changed to the helical cut gear. Call Met's machine 419-522-4111. They do all my machine work and they real big in smoker tractors. They also have a website you can get on and check out. Buy a 6.7 crank if you are going all fresh. It is a 4.9mm stroke so you would have to do custom pistons, rods, or a deckplate.